/**
 * This jQuery plugin displays pagination links inside the selected elements.
 *
 * @author Gabriel Birke (birke *at* d-scribe *dot* de)
 * @version 1.2
 * @param {int} maxentries Number of entries to paginate
 * @param {Object} opts Several options (see README for documentation)
 * @return {Object} jQuery Object
 */
jQuery.fn.pagination = function(maxentries, opts){
opts = jQuery.extend({
items_per_page:10,
num_display_entries:10,
current_page:0,
num_edge_entries:0,
link_to:"#",
prev_text:"Prev",
next_text:"Next",
ellipse_text:"...",
prev_show_always:true,
next_show_always:true,
callback:function(){return false;}
},opts||{});

return this.each(function() {
/**
* Calculate the maximum number of pages
*/
function numPages() {
return Math.ceil(maxentries/opts.items_per_page);
}

/**
* Calculate start and end point of pagination links depending on 
* current_page and num_display_entries.
* @return {Array}
*/
function getInterval()  {
var ne_half = Math.ceil(opts.num_display_entries/2);
var np = numPages();
var upper_limit = np-opts.num_display_entries;
var start = current_page>ne_half?Math.max(Math.min(current_page-ne_half, upper_limit), 0):0;
var end = current_page>ne_half?Math.min(current_page+ne_half, np):Math.min(opts.num_display_entries, np);

if(end - start > opts.num_display_entries + 1 ){
end = start + opts.num_display_entries + 1;
}
return [start,end];
}

/**
* This is the event handling function for the pagination links. 
* @param {int} page_id The new page number
*/
function pageSelected(page_id, evt){
current_page = page_id;
drawLinks();
var continuePropagation = opts.callback(page_id, panel);
if (!continuePropagation) {
if (evt.stopPropagation) {
evt.stopPropagation();
}
else {
evt.cancelBubble = true;
}
}
return continuePropagation;
}

/**
* This function inserts the pagination links into the container element
*/
function drawLinks() {
panel.empty();
var interval = getInterval();
var np = numPages();
// This helper function returns a handler function that calls pageSelected with the right page_id
var getClickHandler = function(page_id) {
return function(evt){ return pageSelected(page_id,evt); }
}
// Helper function for generating a single link (or a span tag if it's the current page)
var appendItem = function(page_id, appendopts){
page_id = page_id<0?0:(page_id<np?page_id:np-1); // Normalize page id to sane value
appendopts = jQuery.extend({text:page_id+1, classes:""}, appendopts||{});
if(page_id == current_page){
var lnk = jQuery("<span class='current'>"+(appendopts.text)+"</span>");
}
else
{
var lnk = jQuery("<a>"+(appendopts.text)+"</a>")
.bind("click", getClickHandler(page_id))
.attr('href', opts.link_to.replace(/__id__/,page_id));


}
if(appendopts.classes){lnk.addClass(appendopts.classes);}
panel.append(lnk);
}
// Generate "Previous"-Link
if(opts.prev_text && (current_page > 0 || opts.prev_show_always)){
appendItem(current_page-1,{text:opts.prev_text, classes:"prev"});
}
// Generate starting points
if (interval[0] > 0 && opts.num_edge_entries > 0)
{
var end = Math.min(opts.num_edge_entries, interval[0]);
for(var i=0; i<end; i++) {
appendItem(i);
}
if(opts.num_edge_entries < interval[0] && opts.ellipse_text)
{
jQuery("<span>"+opts.ellipse_text+"</span>").appendTo(panel);
}
}
// Generate interval links
for(var i=interval[0]; i<interval[1]; i++) {
appendItem(i);
}
// Generate ending points
if (interval[1] < np && opts.num_edge_entries > 0)
{
if(np-opts.num_edge_entries > interval[1]&& opts.ellipse_text)
{
jQuery("<span>"+opts.ellipse_text+"</span>").appendTo(panel);
}
var begin = Math.max(np-opts.num_edge_entries, interval[1]);
for(var i=begin; i<np; i++) {
appendItem(i);
}

}
// Generate "Next"-Link
if(opts.next_text && (current_page < np-1 || opts.next_show_always)){
appendItem(current_page+1,{text:opts.next_text, classes:"next"});
}
}

// Extract current_page from options
var current_page = opts.current_page;
// Create a sane value for maxentries and items_per_page
maxentries = (!maxentries || maxentries < 0)?1:maxentries;
opts.items_per_page = (!opts.items_per_page || opts.items_per_page < 0)?1:opts.items_per_page;
// Store DOM element for easy access from all inner functions
var panel = jQuery(this);
// Attach control functions to the DOM element 
this.selectPage = function(page_id){ pageSelected(page_id);}
this.prevPage = function(){ 
if (current_page > 0) {
pageSelected(current_page - 1);
return true;
}
else {
return false;
}
}
this.nextPage = function(){ 
if(current_page < numPages()-1) {
pageSelected(current_page+1);
return true;
}
else {
return false;
}
}
// When all initialisation is done, draw the links
drawLinks();
        // call callback function
        opts.callback(current_page, this);
});
}